1910] on Colours of Sea and Sky. Ill 



reason to anticipate that this general condusion will be upset, it 

 should not be overlooked that a molecule, especially a diatomic 

 molecule, can hardly Ije supposed to behave as if it were the dielectric 

 sphere of theory. Questions are here suggested for whose decision 

 the time is perhaps not yet ripe. 



[R.] 



P.S. — The (juestion of the colour of the Mediterranean and other 

 waters was long ago discussed by Mr. J. Aitken— an excellent 

 observer — in Proc. Roy. Soc. Edin. 1881-82. His principal con- 

 clusions are very similar to my own. Mr. Aitken rightly insists upon 

 the influence of the colour of the suspended matter to which the 

 return of the light is due. Only when this is white, has the proper 

 colour of the water a full chance of manifesting itself. From the 

 heights of Capri, 1 noticed that the shallow water near the shore 

 showed decidedly green, an effect attributed to the yellowness of the 

 underlying sand. 



